Purpose: This study aimed to evaluate the survival probability of four narrow-diameter
implant systems when subjected to fatigue loading. Materials and Methods: Seventy-two
narrow-diameter implants to be restored with single-unit crowns were divided into
four groups (n = 18): Astra Tech (3.5-mm diameter), with a standard connection (ASC);
BioHorizon (3.4-mm diameter), with a standard connection (BSC); Intra-Lock (3.4-mm
diameter), with a standard multilobular connection (ISC); and Intra-Lock (3.4-mm diameter),
with a modified square connection (IMC). The corresponding abutments were screwed
onto the implants, and standardized metal crowns (maxillary central incisors) were
cemented and subjected to step-stress accelerated life testing in water. Use-level
probability Weibull curves and reliability for 100,000 cycles at 150 and 200 N (90%
two-sided confidence intervals) were calculated. Polarized light and scanning electron
microscopes were used to access the failure modes. Results: The calculated survival
probability for 100,000 cycles at 150 N was approximately 93% in group ASC, 98%
in group BSC, 94% in group ISC, and 99% in group IMC. At 200 N, the survival rate
was estimated to be approximately < 0.1% for ASC, 77% for BSC, 34% for ISC, and
93% for IMC. Abutment screw fracture was the main failure mode for all groups.
Conclusions: Although the probability of survival was not significantly different
among systems at a load of 150 N, a significant decrease was observed at 200 N for
all groups except IMC. Int J Prosthodont 2014;27:359–362. doi: 10.11607/ijp.3926

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